Examples of the prehistoric musical instrument have been discovered in more than 50 countries. The oldest dates back to around 4,000 years and was found in Vietnam by George Condomina, a French Ethnologist in 1949.

The word lithophones is derived from litho, meaning rock, and phone, which means sound. They are still used as percussion instruments today, carved out of large pieces of rock.

There are also several examples of "living" lithophones around the world, made from stalactites and stalagmites.

Mfangano Island, in Lake Victoria, Kenya, the Great Stalacpipe Organ of Luray Caverns, Virginia, Tenkasi in South India and Ringing Rocks Park in Pennsylvania all contain lithophones made from natural rock formations.

There is also a working lithophone in the UK, located in the Keswick Museum. Joseph Richardson's Rock Harmonicon was built in the 19th century, using slate and can still be played by visitors.

Stonehenge may have been the ancient world's largest xylophone, according to researchers. Researchers from the Royal College of art discovered that the monument's central stones produce certain notes when struck – which might be intentional.

The Landscape and Perception Project at RCA aims to "observe and listen to this prehistoric landscape as if with Stone Age eyes and ears."

"There's lots of different tones, you could play a tune," principal investigator Paul Devereux told the BBC. "In fact, we have had percussionists who have played proper percussion pieces off the rocks." The researchers claim that the neolithic stones show evidence of having been struck, drawing a line between Stonehenge and "ringing rocks" in other cultures.

"You can almost see them as a pre-historic glockenspiel, if you like," said Devereux. "And soundscapes of pre-history are something we're really just beginning to explore."